Heretofore, palladium-containing catalysts have found considerable utility in commercial applications because they exhibit sufficient activity in thorough hydrogenation of unsaturated hydrocarbon compounds and retain this activity intact over protracted use. It is known, however, that for the purpose of partial (selective) hydrogenation of diolefins, these catalysts are used as combined or alloyed with some other metals because they exhibit excessive activity and insufficient selectivity. Examples of such a deficiency is seen in a method for the production of cyclopentene by the partial hydrogenation of cyclopentadiene by the use of a catalyst having palladium and iron carried on alumina or magnesium oxide (Japanese Patent Publication SHOWA 52[1977]-33,627 and Japanese Patent Application Laid-open SHOWA 49[1974]-88,837) and in a method for the production of a cyclic olefin by the hydrogenation of a cyclic diene by the use of a palladium-ruthenium alloy having a ruthenium content of 1 to 11% by weight or a palladium-rhodium alloy having a rhodium content of 1 to 5% by weight as a catalyst (Japanese Patent Publication SHOWA 53[1978]-24,938).
The method which uses a supported catalyst of palladium and iron, however, is such that the catalyst used therein has insufficient activity and selectivity, although it is improved in selectivity over a supported catalyst exclusively of palladium. Then, the method which uses the palladium-ruthenium alloy or the palladium-rhodium alloy as a catalyst is such that the catalyst used therein exhibits lower activity than the supported catalyst and entails the problem that it acquires improvement in activity at a sacrifice of selectivity.
It is an object of this invention to overcome the disadvantages as described above in the conventional production of monoolefins by the partial hydrogenation of diolefins.